SOMATOSENSORY EVOKED-POTENTIALS RECORDED DIRECTLY FROM HUMAN THALAMUS AND SM-I CORTICAL AREA

Somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded from the nucleus ventralis caudalis. They consisted of monophasic or diphasic potentials with mean onset latency of 13.8 ms. More complex SE Ps to median nerve stimulation were obtained from the cortex. The SE Ps consisted of two major positive waves, P1 and P2, and were recorded over both the precentral and postcentral gyri, suggesting that somatosensory information converges to the motor cortex, probably to be used for the integration of critical motor activity. In two patients, it was noted that the motor representation of facial movements was larger than the correspondent sensory representation on the postcentral gyrus. This larger motor representation of the face and more specifically of the lips and tongue may be related to human acquisition of mimicry and articulation of language. © 1979, American Medical Association. All rights reserved.